Refusable fuseholder



Dec. 20, 1955 s, R, sMlTH, JR 2,727,961

REFUSBLE FUSEHOLDER Filed April 19, 1954 United States Patent O REFUSABLE rUsEHoLDER Sidney R. Smith, Jr., Stockbridge, Mass., assignor to General Electric Company, a corporation of New York Application April 19, 1954, Serial No. 423,876

1 Claim. (Cl. 200-131) This invention relates to a fuseholder or fuse tube, and more particularly, to a refusable fuseholder or fuse tube.

It is an object of this invention to provide an inexpensive refusable fuseholder or fuse tube having maximum bursting strength and minimum dimensions for a given current interrupting rating.

My invention comprises a refusable fuseholder comprising an interior tubular arc extinguishing gas evolving liner positioned within an outer tubular member, said outer tubular member comprising glass fibers orientated primarily circumferentially and longitudinally with respect to said liner, said fibers impregnated and bonded together by a resin.

The features of my invention which I believe to be novel are set forth with particularity in the appended claim. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing.

In the drawing, Fig. l is an elevational View, partly in section, of one form of my invention. Fig. 2 is a perspective view of my invention during one step in the manufacture thereof.

Referring now to the drawing, and more particularly to Fig. 1, shown therein is a refusable or reusable fuseholder or fuse tube comprising an inner liner or tubular member 1 adapted to evolve electrical arc extinguishing gases when subjected to an electrical arc. Said liner can be constructed out of vulcanized rag fiber, as is well known in the art. Liner 1 is primarily an electrical arc extinguishing gas generating means and does not impart much strength to the fuseholder.

Liner 1 is positioned Within an outer tubular member or covering 2 which imparts maximum bursting strength to the fuseholder at a given current interrupting rating with minimum fuseholder dimensions. Tubular member or covering 2 is constructed out of glass fibers. Said fibers are arranged primarily circumferentially and longitudinally or axially of the liner 1, and are impregnated and bonded together by a resin, such as melamine, polyester, silicone, or phenolic resins.

One method of forming the fuseholder is illustrated in Fig. 2. The outer circumferential surface of liner 1 is knurled or has minute random indentations 3 formed therein. A woven glass cloth or fabric 4 is impregnated or wetted with a resin and then wound around the liner 1 to the desired thickness. Thereafter, the resulting tube is compacted in a die under pressure and cured by the application of heat. By virtue of the knurls or random indentations 3, the covering 2 and liner 1 are intimately secured and bonded together. The glass cloth or fabric 4 is wound about the liner 1 in such a manner whereby the fibers 5 thereof are disposed primarily circumferentially and longitudinally or axially of the liner 1.

The resin impregnated glass liber covering 2 has good machining characteristics and the upper exterior end thereof has threads formed thereon. Removably secured to said upper end is an interiorly threaded cylindrical contact or sleeve 6. The upper exterior end of sleeve 6 is threaded and has an interiorly threaded contact cap 7 removably secured thereto whereby the upper end of the fuseholder is closed. The lower end of the fuseholder is open and has a contact 8 secured adjacent thereto.

Positioned within the fuseholder is a replaceable fuse link electrically connected at its opposite ends to the fuseholder contacts 6, 7, and 8. The fuse link comprises two portions or terminals 9 and 10 connected together by a fusable portion 11 and a strain wire 12. A kraft or rag paper fuse link auxiliary tube 13 surrounds the fusable portion 11 and a substantial length of the fuse link. The upper end of the fuse link makes electrical contact with the contact 6, 7 by virtue of a fuse link button head 14 clamped therebetween, and the lower end of the fuse link extends out of the open end of the fuseholder and is secured to the contact 8.

When the spaced fuseholder contacts 6, 7, and 8 span and make electrical contact with two other spaced contacts, an electrical circuit is completed therebetween by the fuse link. Upon a predetermined overcurrent the fusable portion 11 will be ruptured and an electrical arc will be established between the two fuse link portions or terminals 9 and 10. Said electrical arc will cause the auxiliary tube 13 to generate electrical arc extinguishing gases. At low overcurrents, the auxiliary tube 13 will confine said gases under high pressure, and said high pressure gases will be effective to interrupt said electrical arc without bursting the auxiliary tube 13. Thereafter, the contact cap 7 can be removed, and after the ruptured fuse link is removed, the fuseholder can be refused with a new fuse link and used again.

At high overcurrents, the auxiliary tube 13 may burst before the electrical arc is extinguished and more gases will be generated from the liner 1 at still higher pressures whereby the high overcurrent electrical arc will be extinguished. Since the upper end of the fuseholder is closed, the gases generated within the fuseholder will be expelled out of the lower open end of the fuseholder. This explosive action contributes toward extinguishment of the electrical arc and may be affective to expel the lower end of the fuse link out of the fuseholder to thereby elongate the electrical arc.

The high pressure gases generated within the fuseholder subject the fuseholder to tremendous stresses directed longitudinally or axially of the fuseholder and tangentially of the circumference of the fuseholder. If the fibers of the covering 2 were oriented at random, some of said fibers would extend radially of the fuseholder. Said radially extending tibers would not contribute much towards the bursting strength of the fuseholder. Accordingly, the fibers 5 are oriented primarily circumferentially and longitudinally or axially of the fuseholder.

Tests have indicated that a glass reinforced fuseholder constructed in accordance with my invention has an interrupting ability approximately twice that of the heretofore used cloth reinforced fuseholders while both of said fuseholders have identical dimensions. Accordingly, my invention provides an inexpensive refusable fuseholder having maximum bursting strength and minimum dimensions for a given current interrupting rating. Furthermore, inasmuch as the fuseholder is provided with an interior gas generating liner, covering 2 need not be impregnated with a resin that will necessarily result in the evolution of electrical arc extinguishing gases therefrom.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be triadev without departing from the invention, and that it is intended by the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What l claim as new andl desire tosecure by Letters Patent of the United States is:

A current interrupting device comprising a refusable fuseholder having a replaceable fuse link therein, said fusehrolderv comprising an inner tubular liner, the outer circumferential surface of said liner having minute random identations formed therein, a resin impregnated glass fabric wrapped around said liner and bonded thereto byl heat and pressure, the fibers of said fabric disposed primarily circumferentially and longitudinally of said liner, said fuse link having two portions connected together by a fusible portion, said fusible portion rupturable in response toa predetermined current therethrough whereby an electrical arc is established between said two portions, said arc causing said liner to evolve electrical arc interrupting gases under high pressures, said fuseholder having a bursting strength sufficient to withstand said high pressures whereby said fuseholder may be reused.

References Cited in the file of this patent UNITED STATES PATENTS 2,279,630 McMahon Apr. 14, 1942 2,328,825 McMahon Sept. 7, 1943 2,358,407 McMahon Sept. 19, 1944 

